JP3925153B2 - Magnetron - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetron used in microwave application equipment such as a microwave oven.
[0002]
[Prior art]
A magnetron is an electron tube that generates microwaves, and since it has a relatively high oscillation efficiency and can easily increase the output, it is widely used as a microwave generation source for microwave application equipment such as microwave ovens.
[0003]
A conventional magnetron will be described below.
[0004]
FIG. 7 is a cross-sectional view of a magnetron used in a conventional general microwave oven. As shown in FIG. 7, a cathode part is disposed at the center of the magnetron. This cathode part is composed of a filament 1 and a center lead 4 connected to both ends of the magnetron via end hats 2 and 3 and a side. A lead 5 is used. Further, an anode portion is formed by the anode cylinder 6 and a plurality of vanes 7 that protrude from the inner peripheral surface of the anode cylinder 6 toward the filament 1 and whose tips are arranged at a predetermined distance from the filament 1. Has been.
[0005]
A pair of mortar-shaped magnetic poles 9 and 10 having substantially the same shape are provided opposite to each other in both ends of the anode cylinder 6 in the tube axis direction. Is provided with an input unit 11 for supplying filament application power and a magnetron driving high voltage, and an output unit 12 for transmitting and radiating microwaves to constitute a main body of the magnetron.
[0006]
Further, the pair of annular permanent magnets 13 and 14 has one magnetic pole surface as the magnetic poles 9 and 10 and the other magnetic pole surface as the frame-shaped yokes 15 and 16 each having a U-shaped cross section made of a ferromagnetic material. Magnetic fields are supplied to an electron motion space 17 formed between the vane 7 and the filament 1 by a magnetic circuit configured to be magnetically coupled. One end of a microwave output antenna lead 18 is connected to an arbitrary vane of the anode structure, and the other end is led out to the outside.
[0007]
The main specifications and dimensions of the main body of the conventional magnetron are as follows: the oscillation frequency is 2,450 MHz, the number of vanes 7 is 10, and the diameter φa of the inscribed circle formed at the cathode side tip of vane 7 is 9.0 mm, the outer diameter φc of the coiled filament 1 is 3.9 mm, the dimensions of the vane 7 are the tube axis height H of 9.5 mm, the thickness T of 2.0 mm, and the cathode side tip of the adjacent vane 7 The distance G between the portions is 0.9 mm, the ratio G / T is G / (G + T) = 0.31, and the magnetic flux density in the electron motion space 17 is at the center between the pair of magnetic poles 9 and 10. When the magnetic flux density on the center lead 4 is measured, it is 0.195 ± 0.010 Tesla.
[0008]
In the magnetron having such a configuration, when the filament 1 is heated and a predetermined voltage is applied between the cathode portion and the anode portion, electrons emitted from the filament 1 toward the vane 7 are converted into an electron motion space 17. The surrounding magnetic field of the Fiment 1 is generated by the internal magnetic field to generate microwave energy. This microwave energy is transmitted to the output unit 12 by an antenna lead 18 electrically coupled to one of the vanes 7 and is radiated into a cabinet such as a microwave oven. The oscillation efficiency of the magnetron at this time is calculated from the measured value of the direct-current input (anode voltage × anode current) applied between the anode part and the cathode part and the microwave power radiated from the output part 12. As a typical magnetron characteristic, an oscillation efficiency of 75% was obtained by outputting a microwave power of about 1 kW at an anode voltage of 4.5 kV and an anode current of 300 mA.
[0009]
Here, the oscillation efficiency of the magnetron is determined by the product of electronic efficiency, which is the kinetic efficiency of electrons, and circuit efficiency related to circuit constants such as Joule loss and dielectric loss. That is, the oscillation efficiency η = electronic efficiency ηe × circuit efficiency ηc.
[0010]
Among these, the electronic efficiency ηe is expressed by (Equation 1) in relation to the anode voltage, and it is known that the electron efficiency ηe is improved when the anode voltage is increased.
[0011]
[Expression 1]
[0012]
From another point of view, the electronic efficiency ηe is expressed by (Equation 2) in relation to the magnetic flux density, and it is known that increasing the magnetic flux density improves the electronic efficiency ηe.
[0013]
[Expression 2]
[0014]
[Problems to be solved by the invention]
The need to improve the oscillation efficiency of the magnetron has arisen due to the demand for improved oscillation efficiency from the recent trend toward energy saving in the world, so in the conventional magnetron, the anode voltage is increased and the electron motion space is increased. The oscillation efficiency has been improved by increasing the magnetic flux density supplied to. However, if the anode voltage is increased, the magnetron drive power supply must be changed to one for high voltage, and the insulation voltage between the magnetron and its peripheral parts must be increased due to the need to increase the anode voltage, which increases costs. Had the problem of inviting.
[0015]
The present invention solves the above-described conventional problems, and an object thereof is to provide a highly efficient magnetron that improves electronic efficiency and improves oscillation efficiency.
[0016]
[Means for Solving the Problems]
In order to solve this problem, a magnetron according to a first aspect of the present invention includes an anode cylinder, an anode section formed of a plurality of vanes fixed to an inner wall surface of the anode cylinder, and the anode section. A cathode portion made of a coiled filament provided in the coaxial central portion, a pair of magnetic poles disposed above and below the anode portion in the tube axis direction, and a magnetic circuit that is magnetically coupled to the pair of magnetic poles. An annular permanent magnet, and an input portion and an output portion respectively disposed on the outer sides in the tube axis direction of the magnetic pole, and the diameter of the inscribed circle of the vane tip portion constituting the anode portion is 7. 5 to 8.5 mm, the outer diameter of the coiled filament is in the range of 3.4 to 3.6 mm, and the gap G between the adjacent cathode side tips of the vane and the thickness of the vane The ratio with T is G / (G + T) = 0.20-0.25 It is.
[0017]
Thereby, the oscillation efficiency can be improved even with the conventional anode voltage.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected about the same component as a prior art example.
[0021]
Fig.1 (a) shows the principal part expanded sectional view of the magnetron of this invention. The dimensions of each part are as follows: the outer diameters of the two annular permanent magnets 19 and 20 are D1 and D3, the inner diameters are D2 and D4, the thicknesses are L1 and L2, the diameter of the inscribed circle on the vane cathode side is φa, and the coil filament The outer diameter of 1 was represented by φc, and the dimension of the vane 7 in the tube axis direction was represented by H. FIG. 1 (b) shows the anode portion when the vane 7 is viewed from the tube axis direction, that is, the A direction in FIG. 1 (a), and the interval between the cathode side tip portions of adjacent vanes is G. The thickness was represented by T. In the present embodiment, the same material and dimensions are used for the two annular permanent magnets. The inventors of the present invention have made the magnetic flux density of the magnetron larger than 0.195 ± 0.010 Tesla in the conventional magnetron for the purpose of increasing the oscillation efficiency of the magnetron according to (Equation 1), and by various experiments. As a result of trial and error, it was set to 0.250 ± 0.010 Tesla. In order to obtain this value, the outer diameters D1 and D3 of Sr ferrite (FB5N manufactured by TDK Corporation) annular permanent magnets were changed from 55 mm to 80 mm. The inner diameters D2 and D4 and the thicknesses L1 and L2 of the annular permanent magnet are the same as the conventional one.
[0022]
In the present invention, as a method of obtaining the same effect as increasing the anode voltage Va in order to increase the oscillation efficiency, the electric field between the anode part and the cathode part is reduced by reducing the diameter φa of the inscribed circle on the vane cathode side tip part. The experiment was carried out using the method of strengthening. In addition, in order to examine the electric field distribution in detail, the mutual spacing G between the cathode side tips of the vane and the thickness T of the vane were examined.
[0023]
FIG. 2 shows the experimental results on the magnitude of the magnetic flux density required to oscillate the same anode voltage Va at 4.5 kV when the diameter φa of the vane cathode side tip inscribed circle is changed. As shown in the figure, when the diameter φa of the inscribed circle on the vane cathode side tip is 8.5 mm, 8.0 mm, and 7.5 mm, the magnetic flux densities are 0.220 ± 0.010 Tesla and 0.250 ±, respectively. It was necessary to increase it to 0.010 Tesla and 0.290 ± 0.010 Tesla. However, the oscillation efficiency of the magnetron at this time is 75.4%, 76.0%, and 75.6%, respectively, as shown in FIG. It was only slightly larger. For comparison, the magnetic flux density (0.195 ± 0.010 Tesla) and the oscillation efficiency (75.75) are also shown in FIGS. 2 and 3 where the diameter φa of the inscribed circle on the vane cathode side in the conventional magnetron is 9.0 mm. 0%). In this embodiment, except for the experiment shown in FIG. 6 to be described later, the height H in the tube axis direction is 9.5 mm, which is the same as the prior art, and the number of vanes 7 is 10, the same as the conventional one, for all experiments. did. As described above, the magnetron oscillation efficiency was slightly improved by increasing the electric field in the electron motion space and increasing the magnetic flux density. However, it was not enough.
[0024]
For this reason, investigations were made to further improve the oscillation efficiency. Then, considering that the magnitude of the electric field and the magnetic flux density is not sufficient, the distribution of the electric field and the magnetic flux density in the axial direction in the electron motion space is considered, and the inside of the vane tip is considered. The outer diameter φc of the coiled filament 1 was changed with respect to the contact circle diameter φa. The result of the oscillation efficiency at that time is shown in FIG. In FIG. 4, as shown in FIG. 2, the inscribed circle diameter φa of the vane tip is set to 7.5 mm, 8.0 mm, and 8.5 mm, and the magnetic flux densities are 0.290 ± 0.010 Tesla, 0.2 mm, respectively. For the ones with 250 ± 0.010 Tesla and 0.220 ± 0.010 Tesla, the outer diameter φc of the coiled filament 1 changed from 3.9 mm to 3.8 mm, 3.7 mm, 3.6 mm, 3.4 mm. The result of the oscillation efficiency is shown. For comparison, φa 9.0 mm and φc 3.9 mm, which are conventional examples, are indicated by black circles (●), and the oscillation efficiency was 75%. The triangle (Δ) indicates the case where the outer diameter φc was changed to 3.9 mm, 3.8 mm, and 3.7 mm, and their oscillation efficiencies were all 76%. A white circle (◯) indicates the case where the outer diameter φc is changed to 3.6 mm and 3.4 mm, and the oscillation efficiency thereof is 77% in all cases. From the above results, the inscribed circle diameter φa of the vane tip is set to 7.5 mm, 8.0 mm, and 8.5 mm, and the magnetic flux densities are 0.290 ± 0.010 Tesla, 0.250 ± 0.010 Tesla, It was found that the oscillation efficiency was 77% when the outer diameter φc was in the range from 3.4 mm to 3.6 mm for 0.220 ± 0.010 Tesla.
[0025]
Furthermore, the distribution of the electric field in the electron motion space is examined in detail, and the mutual distance G and the thickness T of the vane on the cathode side tip of the vane are examined. In FIG. 5, when the inscribed circle diameter φa of the vane tip is 8.0 mm, the magnetic flux density is 0.250 ± 0.010 Tesla, and the outer diameter φc of the coiled filament 1 is 3.6 mm, G and The results of measuring the oscillation efficiency using the T ratio G / (G + T) as a parameter are shown. When G / (G + T) = 0.20, 0.22, and 0.25, the oscillation efficiency was improved to 77.8%, 78.1%, and 77.5%, respectively, with the average value of 10 samples.
[0026]
Further, since the oscillation efficiency is lowered when an electric field is generated in the height direction of the vane, the height H of the vane 7 in the tube axis direction was examined. FIG. 6 shows the results shown in FIGS. 2 to 5 under the conditions when the oscillation efficiency is maximum, that is, the magnetic flux density is 0.250 ± 0.010 Tesla, the inscribed circle at the tip of the vane. The result of examining the height H in the tube axis direction of the vane 7 when the diameter φa is 8.0 mm, the outer diameter φc of the coiled filament 1 is 3.6 mm, and G / (G + T) = 0.22 is shown. From this figure, it has been found that the oscillation efficiency is approximately 78% when the height dimension H of the vane 7 in the tube axis direction is 9.0 mm or more.
[0027]
Table 1 compares the present invention and a conventional magnetron, and shows measurement results of output and oscillation efficiency at an input anode voltage of 4.5 kV and an anode current of 300 mA.
[0028]
[Table 1]
[0029]
【The invention's effect】
As described above in detail, the present invention improves the electronic efficiency ηe without increasing the anode voltage by increasing the magnetic flux density and optimizing the dimensions of each part of the magnetron related to the electron motion space, and the oscillation efficiency η It is possible to provide a high-efficiency magnetron that can greatly improve the above.
[Brief description of the drawings]
FIG. 1A is an enlarged cross-sectional view of a main part of a magnetron of the present invention, and FIG. 1B is a diagram showing a mutual interval G between the cathode side tips of adjacent vanes and a thickness T of the vanes of the present invention. FIG. 3 is a diagram showing the relationship between the diameter of the inscribed circle at the vane tip and the magnetic flux density in comparison with the prior art in the present invention. FIG. 4 is a graph showing the efficiency of oscillation efficiency between the diameter φa of the inscribed circle at the vane tip and the outer diameter φc of the coiled filament in comparison with the prior art. FIG. 6 is a graph showing the relationship between the ratio of the gap G to the thickness T at the vane cathode side tip and the oscillation efficiency in comparison with the conventional example. FIG. 6 shows the relationship between the height in the vane tube axial direction of the present invention and the oscillation efficiency. [Fig. 7] Cross-sectional view of a conventional magnetron [Explanation of symbols]
1 coiled filament 4 center lead 6 anode cylinder 7 vane 9 magnetic pole 10 magnetic pole 17 electron motion space 19 annular permanent magnet 20 annular permanent magnet D1 annular permanent magnet outer diameter D2 annular permanent magnet inner diameter D3 annular permanent magnet outer diameter D4 annular Inner diameter L1 of permanent magnet Thickness L2 of annular permanent magnet Thickness of annular permanent magnet φa Diameter of vane cathode side tip inscribed circle φc Outer diameter G of coiled filament T Thickness H Vane's axial dimension

Claims (1)

An anode portion formed of an anode cylinder and a plurality of vanes fixed to the inner wall surface of the anode cylinder; a cathode portion formed of a coiled filament provided in a coaxial central portion of the anode portion; and the anode A pair of magnetic poles disposed above and below the tube axis in the tube axis, an annular permanent magnet that is magnetically coupled to the pair of magnetic poles to form a magnetic circuit, and an outer side of each of the magnetic poles in the tube axis direction. An input part and an output part provided, the diameter of the inscribed circle of the vane tip part constituting the anode part is in the range of 7.5 to 8.5 mm, and the outer diameter of the coiled filament is The ratio of the gap G between the adjacent cathode side tips of the vane and the thickness T of the vane is within the range of 3.4 to 3.6 mm, and G / (G + T) = 0.20 to 0.25. magnetron, characterized in that the the.

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